The present invention relates to an apparatus for arc welding or plasma cutting with a current source as well as a set of controls to influence the welding or cutting process respectively.
The known apparatus of this type essentially consists of a housing in which a construction unit (transformer, rectifier, frequency converter and the like) is provided to produce the welding current and the welding voltage. Moreover, controls are provided in addition to the welding current and welding voltage regulating devices inside the housing by means of which certain control functions are undertaken when operating the welding current source. In case the arc welding apparatus is constructed as a shielded arc welding apparatus with an ablating or consummable electrode, a wire feed roll as well as a wire feed is additionally provided near or in the current source. The controls include in a shielded arc welding apparatus as a rule the following functions:
two cycle control PA1 four cycle control PA1 contact ignition (scratch ignition) PA1 spot welding.
A two cycle control relates to a control in which during the first cycle (torch switch depressed) the gas flows, the welding voltage reaches the wire electrode and starts the wire motion. During the second cycle (torch switch released) gas, welding voltage and wire motion are switched off.
A four cycle control relates to a control in which during the first cycle (torch switch depressed) the gas flows and the welding voltage reaches the wire electrode. During the second cycle (torch switch released), the wire motion starts up. The third cycle (torch switch depressed) causes the welding voltage and the wire motion to be switched off. During the fourth cycle (torch switch released) the gas is switched off.
In scratch ignition, the torch switch is depressed and released as a result of which the welding voltage reaches the electrode. When touching the workpiece, the gas and wire feed are switched on. When pulling the arc, the gas and wire feed are switched off. In spot welding, the torch switch is depressed and released as a result of which the gas flows, the welding voltage reaches the wire electrode and then the wire feed starts up. The termination of spot welding takes place by means of a time interval relay with which after completion of the set time interval the wire feed welding voltage and gas flow are turned off.
As can be seen in the description of the above mentioned control function, gas valves, the motor of the wire feed as well as current relay and solenoid are controlled with the controls in periodic independence of each other. In order to guarantee an optimal functioning of the controls and consequently of the entire welding apparatus it is, therefore, expedient to test the machines, especially the controls as well as the units controlled by the controls, from time to time for their functionality (maintenance).
It is, moreover, necessary, in addition to the maintenance, in order to detect defects during repair work to test the individual control functions, the controlled components as well as the complete controls with respect to incoming and outgoing signals to be able to localize the defects which occurred.
This work was carried out thusfar with current and voltage indicating instruments.